1. Field of the Invention
The present invention relates to the general technical field of agricultural machinery. It relates more particularly to a working element of an agricultural machine intended to be mounted on a substantially horizontal beam by means of a linking structure comprising at least one upper arm and at least one lower arm, said working element being subjected on one hand to a depth control force directed toward the ground and on another hand to a ballasting exerted by a ballasting device comprising at least one spring.
The invention also concerns agricultural apparatuses fitted with a working element according to the invention. It relates also to an agricultural seed drill fitted with one or more working elements as described above.
2. Discussion of the Background
This type of working element is known in U.S. Pat. No. 5,555,824. This document relates to a precision seed drill comprising several of these working elements. The working elements are provided with disks making it possible to form furrows in the ground into which the seeds will be inserted. The working elements are connected to the frame of the seed drill by means of a respective linking structure which is mounted on a beam. The linking structure comprises two lower arms and two upper arms.
The disks are subject to the weight of the working element which carries them to ensure that the furrow is formed to a required depth. Additionally, each working element is loaded with a ballasting device to facilitate the insertion of the disk into the ground. The ballasting of the working element is performed by means of springs connected between the upper arms and the lower arms. The springs are in particular connected to a support provided with two locking levers. The position of the support can be adjusted by means of different holes made in the upper arms to change the ballasting. The support also comprises, in its central part, a handle used to modify the ballasting according to a fine and continuous adjustment.
The ballasting of the working elements is modified individually and by moving the support from one hole to a different hole. Accordingly, the support guided on either side by the upper arms, slides over the latter until the required adjustment is obtained. Next the two levers must be engaged in a respective hole. Since the support has a width equal to the distance between said upper arms and comprises on either side surfaces for guidance, the user has to feel to engage the two locking levers in the required holes because visibility is not sufficient.
In addition, to obtain a uniform germination of the seeds, each working element mounted on the seed drill beam must be loaded in the same manner. This is not easily done partly because on each working element is mounted a hopper containing seeds which empties gradually as the seed drill advances and partly because of the use of the fine adjustment of the handle placed on the support. It is therefore not obvious to ballast the various working elements in the same manner.